Polarized light source device and back light module for liquid crystal display

ABSTRACT

A polarized light source device comprises a light source, a reflector, a transparent substrate, an antireflection layer, and a plurality of metal grid wires. The reflector surrounds the light source for reflecting the light, and has an opening for emitting the light. The transparent substrate is disposed at the opening. The antireflection layer is disposed on the transparent substrate. The metal grid wires are disposed on the antireflection layer for transmitting the light with a predetermined polarization therethrough.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of Taiwan patentapplication serial no. 091125380, filed Oct. 23, 2002 and Taiwan patentapplication serial no. 091136762, filed Dec. 16, 2002, and the fulldisclosures thereof are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to a polarized lightsource device, and more particularly, to a back light module for aliquid crystal display (LCD) which provides polarized light with hightransmittance.

[0004] 2. Description of the Related Art

[0005] Referring to FIG. 1, it depicts the structure of a conventionalliquid crystal display. Generally, the liquid crystal display deviceincludes a liquid crystal display panel 10 which has two substrates anda liquid crystal material sealed therebetween, a back light unit 20disposed under the liquid crystal display panel 10, and cases 11 and 12.

[0006] The back light unit 20 is utilized to distribute the light from alight source uniformly over the surface of the liquid crystal displaypanel 10. There are several kinds of back light units 20 such as adirect back light type (or direct type) and an edge light type.

[0007] Referring to FIG. 2, it is a cross-sectional view along line 2-2of FIG. 1 and depicts a back light module 21 of the direct type. Thedirect type back light module 21 includes a housing 70 which has areflective sheet 60 disposed on the bottom surface of the housing 70, alamp 50, such as a fluorescence cathode tube, disposed at the bottomportion of the housing 70, a diffusing sheet 40 disposed on the uppersurface of the housing 70 and a prism sheet 30 disposed on the diffusingsheet 40.

[0008] Referring to FIG. 3, it is a cross-sectional view along line 2-2of FIG. 1 and depicts a back light module 22 of the edge light type. Theedge light type back light module 22 includes a light guide 80, a lamp50 which is attached to at least one edge of the light guide 80, and aU-shaped reflector 61 which surrounds the lamp 50. An open portion ofthe reflector 61 is disposed at the edge of the light guide 80, areflecting sheet 60 is disposed at the bottom of the light guide 80, adiffusing sheet 40 is disposed on the light guide 80 and a prism sheet30 is disposed on the diffusing sheet 40. Because the lamp 50 isdisposed at the edge of the light guide 80, the thickness of the LCD canbe relatively decreased.

[0009] The light guide 80 includes a printed dot pattern or a V-shapednotched pattern 82 on at least one surface for scattering the light inthe light guide 80 and illuminating the liquid crystal display panel 10.The light guide 80 and the dot pattern or V-shaped notched pattern 82thereon are typically made of PMMA by the process of press or ejectionmolding. The diffusing sheet 40 is disposed on the light guide 80 andtypically made of half-transparent PET or polycarbonate for furtherevenly diffusing the light emitted from the light guide 80. The prismsheet 30 is disposed on the diffusing sheet 40 for gathering thediffused light from the diffusing sheet 40 in the directionperpendicular thereto.

[0010] Since the liquid crystal display panel 10 has a polarizing sheetfor transmitting the light with one polarizing direction and absorbingthe light with the other polarizing direction, about 50% of the energyof the light is lost when the light passes the polarizing sheet.Therefore, a polarization recycle film 35 is typically disposed on theprism sheet 30 for reflecting the light with the other polarizingdirection, and the reflected light then is reflected by the opticalelement therebeneath and recycled after the polarizing direction thereofis changed, thereby increasing the brightness of the liquid crystaldisplay. However, the above-mentioned polarization recycle film isavailable typically from 3M™ Company of St. Paul Minn. under the tradename Dual Brightness Enhancement Film (DBEF), which causes the liquidcrystal display up to 160-170% brighter, but is significantly expansive.Further, the cost of the liquid crystal display will increase more andmore as the dimension of the liquid crystal display increases in recentyears.

[0011] Generally, the back light module of the liquid crystal displayshall be constructed to meet the requirements of increasing powerefficiency and the screen brightness, providing uniform brightness,lowering power consumption and cost, as well as decreasing thedimension. Prior art attempts have been made to meet the requirementsand, for example, can be seen in U.S. Pat. No. 6,164,790 issued to Leeon Dec. 26, 2000, U.S. Pat. No. 5,477,422 issued to Hooker et al. onDec. 19, 1995, and U.S. Pat. No. 5,485,354 issued to Ciupke et al. onJan. 16, 1996. These patents are all incorporated herein by reference.

[0012] Japan Patent Application No. 11(1999)-233919, which isincorporated herein by reference, discloses a fluorescent lamp withreflective film for a back light module of a liquid crystal display soas to avoid the inter-reaction between the adjacent lamps and furtheravoid the decrement of illumination due to the inter-reaction.

[0013] Furthermore, U.S. Pat. No. 6,122,103 issued to Perkins on Sep.19, 2000 entitled “Broadband Wire Grid Polarizer For The VisibleSpectrum”, which is incorporated herein by reference, discloses apolarizer with metal grid wires, which provides high transmittance andreflectance for the entire visible spectrum.

[0014] U.S. patent application Ser. No. 10/227841 entitled “Panel LightSource Device And Back Light Module For Liquid Crystal Display Device”,filed on Aug. 27, 2002 and commonly assigned to the assignee of thepresent application, discloses a back light module with metal grid wiresand is incorporated herein by reference.

[0015] The conventional metal grid wire polarizer 90 substantiallycomprises a transparent substrate 92 made of glass and metal grid wires94 disposed thereon, as shown in FIG. 4. Now referring to FIG. 5, itdepicts the graphic plot of transmittance Tp, Ts and the reflectance Rp,Rs of the P-polarization (polarizing direction perpendicular to themetal grid wires 94) and S-polarization (polarizing direction parallelto the metal grid wires 94) of the metal grid wires 94 versus the ratioΩ of the width W to the pitch P of the metal grid wires 94, where thethickness T of the metal grid wires 94 is about 0.1 μm and thewavelength of the incident light is about 0.545 μm (green light).Although the metal grid wires are easy to manufacture in the range ofthe ratio Ω from 0.5 to 0.6, the transmittance Tp of the P-polarization(polarizing direction perpendicular to the metal grid wires) of themetal grid wires 94 is comparatively low, as shown in the drawing.

[0016] Accordingly, there exists a need for a light source and/or a backlight module of a liquid crystal display capable of meeting theabove-mentioned requirements.

SUMMARY OF THE INVENTION

[0017] It is an object of the present invention to provide a polarizedlight source for providing the liquid crystal display with the polarizedlight so as to increase the energy efficiency of the liquid crystaldisplay.

[0018] It is another object of the present invention to provide a backlight module for providing the liquid crystal display with the polarizedlight so as to increase the energy efficiency of the liquid crystaldisplay.

[0019] In order to achieve the above objects, the present inventionprovides a polarized light source device comprising a light source, areflector, a transparent substrate, an antireflection layer, and aplurality of metal grid wires. The reflector surrounds the light sourcefor reflecting the light, and has an opening for emitting the light. Thetransparent substrate is disposed at the opening. The antireflectionlayer is disposed on the transparent substrate. The metal grid wires aredisposed on the antireflection layer for transmitting the light with apredetermined polarization therethrough.

[0020] The present invention further provides a polarized light sourcecomprising an illuminant, a reflective film, and a plurality of metalgrid wires. The reflective film surrounds the illuminant and has anopening for emitting the light. The metal grid wires are disposed at theopening for transmitting the light with a predetermined polarizationtherethrough.

[0021] The polarized light source according to the present invention canbe attached to a liquid crystal display for illuminating a liquidcrystal display panel of the liquid crystal display.

[0022] Accordingly, the back light module or the polarized light sourceaccording to the present invention includes a polarizing element andthus provides the polarized light without lowering the energyefficiency. Also, the polarized light may be transmitted through thepolarizing film of the liquid crystal display to minimize the lightabsorbed by the polarizing film. Therefore, the back light module or thepanel light source according to the present invention dispenses with theexpensive optical film and still meets the requirements of increasingthe entire power efficiency, increasing the brightness, and lowering thecost of the liquid crystal display.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other objects, advantages, and novel features of the inventionwill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawing.

[0024]FIG. 1 is a perspective exploded schematic view of a liquidcrystal display according to the prior art.

[0025]FIG. 2 is a cross sectional schematic view along line 2-2 of FIG.1 of a direct type back light module according to the prior art.

[0026]FIG. 3 is a cross sectional schematic view along line 2-2 of FIG.1 of an edge light type back light module according to the prior art.

[0027]FIG. 4 is a cross sectional schematic view of a conventional metalgrid wire polarizer.

[0028]FIG. 5 is a graphical plot showing the relationship between theratio Ω of the width to the pitch of the metal grid wires shown in FIG.4, and the transmittance and the reflectance thereof.

[0029]FIG. 6 is a cross sectional schematic view of a polarized lightsource device according to an embodiment of the present invention.

[0030]FIG. 7 is a cross sectional schematic view of a polarized lightsource device according to another embodiment of the present invention.

[0031]FIG. 8 is a partial enlarged cross sectional schematic view of apolarizer of the polarized light source device shown in FIG. 6.

[0032]FIG. 9 is a graphical plot showing the relationship between theratio Ω of the width to the pitch of the metal grid wires shown in FIG.6, and the transmittance and the reflectance thereof.

[0033]FIG. 10 is a cross sectional schematic view of a liquid crystaldisplay using the polarized light source device according to the presentinvention.

[0034]FIG. 11 is a cross sectional schematic view of another liquidcrystal display using the polarized light source device according to thepresent invention.

[0035]FIG. 12 is a cross sectional schematic view of a lamp according toan embodiment of the present invention.

[0036]FIG. 13 is a cross sectional schematic view of a lamp according toanother embodiment of the present invention.

[0037]FIG. 14 is a partial enlarged perspective schematic view of metalgrid wires of the lamp shown in FIG. 12.

[0038]FIG. 15 is a cross sectional schematic view of a liquid crystaldisplay using the lamp according to the present invention.

[0039]FIG. 16 is a cross sectional schematic view of another liquidcrystal display using the lamp according to the present invention.

DESCRIPTION OF THE EMBODIMENT

[0040] Referring to FIG. 6, it depicts a polarized light source device100 according to an embodiment of the present invention. The polarizedlight source device 100 comprises a light source, such as a lamp 150, areflector 161 surrounding the lamp 150, and a polarizer 192. The lamp150 can be a cold cathode fluorescent lamp (CCFL).

[0041] Now referring to FIG. 8, it depicts the polarizer 192 of thepolarized light source device 100. The polarizer 192 comprises atransparent substrate 194, an antireflection layer 191 disposed on thetransparent substrate 194, and metal grid wires 190 disposed on theantireflection layer 191. Light emitted from the lamp 150 is transmittedinto the transparent substrate 194, through the antireflection layer191, and out of the metal grid wires 190. The transparent substrate 194is made of transparent material, such as glass and acrylic resin (PMMA),the refractive index of which is n_(s). The antireflection layer 191 ismade of transparent dielectric material, such as nitrogen silicide(Si—Nx), the refractive index of which is n_(m). The antireflectionlayer 191 shown in the drawing is a single film coated on thetransparent substrate 194, but it will be apparent to those skilled inthe art that the antireflection layer 191 can be a multi-layer filmcoated on the transparent substrate 194. The refractive index of theantireflection layer 191 is in the range between the refractive indexn_(s) of the transparent substrate 194 and the equivalent refractiveindex n_(a) of the metal grid wires 190, i.e. n_(s)>n_(m)>n_(a).Preferably, the refractive index n_(m) of the antireflection layer 191is derived from the following equation:

n _(m)≈{square root}{square root over ((n _(a) ×n _(s)))}

[0042] The thickness d of the antireflection layer 191 is derived fromthe following equation:

d≈¼×λ/n _(m)

[0043] where λ is the wavelength of the incident light.

[0044] In fact, the transparent substrate 194 is made of glass or PMMA,and thus the antireflection layer 191 should be made of the material ofwhich the refractive index is above about 1.5.

[0045] The metal grid wires 190 are parallel to the lamp 150, and spacedout and formed on the antireflection layer 191 such that the light withthe polarizing direction perpendicular to the metal grid wires 190(P-polarization), i.e. perpendicular to the longitudinal direction ofthe lamp 150, is transmitted and the light with the polarizing directionparallel to the metal grid wires 190 (S-polarization) is reflected.

[0046] According to the present invention, the metal grid wires 190 aremade of aluminum (Al), silver (Ag), copper (Cu) or alloy, and preferablyare made of aluminum. Preferably, the pitch P of the metal grid wires190 is below about 300 nm, the thickness T of the metal grid wires 190is in the range from about 30 nm to about 200 nm, and the ratio of thewidth W to the pitch P of the metal grid wires 190 is in the range fromabout 0.1 to about 0.8.

[0047] Now referring to FIG. 9, it depicts the graphic plot oftransmittance Tp, Ts and the reflectance Rp, Rs of the P-polarization(polarizing direction perpendicular to the metal grid wires 190) andS-polarization (polarizing direction parallel to the metal grid wires190) of the polarizer 192 versus the ratio Ω of the width W to the pitchP of the metal grid wires 190. The transparent substrate 194 is made ofglass, the thickness T of the metal grid wires 190 is about 0.1 μm, thewavelength of the incident light is about 0.545 μm (green light), andthe antireflection layer 191 is made of nitrogen silicide (Si—Nx) andthe thickness d of the antireflection layer 191 is 70 nm. As shown inthe drawings, the transmittance Tp of the P-polarization (polarizingdirection perpendicular to the metal grid wires 194) of the metal gridwires 190 is raised because of the existence of the antireflection layer191 when the ratio Ω is in the range from 0.5 to 0.6.

[0048] Now referring to FIG. 7, it depicts a polarized light sourcedevice 100′ according to another embodiment of the present invention.The polarized light source device 100′ is similar to the polarized lightsource device 100 and comprises a lamp 150′, a reflector 161′surrounding the lamp 150′, and a polarizer 192′. The polarizer 192′ hasmetal grid wires 190′. The metal grid wires 190′ are perpendicular tothe lamp 150′, and spaced out and formed on the antireflection layer191′ such that the light with the polarizing direction perpendicular tothe metal grid wires 190′ (P-polarization), i.e. parallel to thelongitudinal direction of the lamp 150, is transmitted and the lightwith the polarizing direction parallel to the metal grid wires 190′(S-polarization) is reflected.

[0049] Referring to FIG. 10, it depicts a liquid crystal display 200using the polarized light source device 100 according to the presentinvention. The liquid crystal display 200 comprises a liquid crystaldisplay panel 210 and a back light module 220. The liquid crystaldisplay panel 210 comprises two transparent substrates 212, 214 andliquid crystal material 216 disposed therebetween. The outer surfaces oftransparent substrates 212, 214 of the liquid crystal display panel 210are covered with polarizing sheets 218, 219, and the inner surfacesthereof are provided with switching elements for changing the alignmentsof the molecular of the liquid crystal material 216 and thus generatingimages.

[0050] The back light module 220 is of an edge light type and is servedas a panel light device for evenly illuminating the liquid crystaldisplay panel 210. The back light module 220 comprises the polarizedlight source device 100 according to the present invention, a wedgelight guide 280 and a plurality of layers of optical films, such asdiffusing sheet 240 and a prism sheet 230. The diffusing sheet 240 isused for further evenly diffusing the light. The prism sheet 230 iscommercially available from 3M™ Company of St. Paul Minn. under thetrade name Brightness Enhancement Film II (BEF II) for gathering thelight in the direction perpendicular thereto.

[0051] The light emitted from the polarized light source device 100 istransmitted into the light guide 280 via an incoming surface 284 of thelight guide 280. The light guide 280 is provided with scatteringelements 182, such as a printed dot pattern or a V-shaped notchedpattern on the bottom surface of the light guide 280, for scattering thelight in the light guides 180 and transmitting the light out of theupper surface or the outgoing surface 285 of the light guide 280 so asto serve as a uniform panel light source. The light guide 280 istypically made of PMMA by the process of press or ejection molding. Thelight guide 280 further comprises reflectors 260, 265 disposed in thebottom surface and the distal end of the light guide 280 for reflectingthe light back to the light guide 280.

[0052] Obviously, it will be apparent to those skilled in the art thatthe polarizing direction of the polarizing sheet 219 on the liquidcrystal display panel 210 is corresponding to that of the polarizedlight source device 100 such that the brightness of the liquid crystaldisplay 200 is increased. Generally speaking, because of the arrangementof the liquid crystal display, the back light module 220 according tothe present invention is particularly adapted to be used with a thinfilm transistor (TFT) liquid crystal display panel ofIn-Plane-Switching, Vertical Alignment, and Multi-Domain VerticalAlignment.

[0053] Referring to FIG. 11, it depicts a liquid crystal display 300using the polarized light source device 100 according to the presentinvention. The liquid crystal display 300 is generally similar to theliquid crystal display 200, wherein the similar elements are designatedwith the similar reference numerals. The liquid crystal display 300comprises a liquid crystal display panel 110 and a back light module320. The back light module 320 is of the direct back light type and isprovided with a plurality of polarized light source device 100 disposedin a housing 370.

[0054] Accordingly, the back light module or the polarized light sourceaccording to the present invention provides the polarized light. Thepolarized light may be transmitted through the polarizing film of theliquid crystal display to minimize the light absorbed by the polarizingfilm. Therefore, the back light module or the panel light sourceaccording to the present invention dispenses with the expensive opticalfilm and still meets the requirements of increasing the entire powerefficiency, increasing the brightness, and lowering the cost of theliquid crystal display.

[0055] Now referring to FIG. 12, it depicts a polarized light source orlamp 550 according to an embodiment of the present invention. The lamp550 is applied to a liquid crystal display, typically is a cold cathodefluorescent lamp (CCFL), and has an elongated tube structure. The lamp550 has a transparent substrate, such as a glass tube 552, a reflectivefilm 554 coated on the inside surface of the glass tube 552, mercuryvapor 558 filling the glass tube 552, and fluorescent material 556disposed between the mercury vapor 558 and the glass tube 552. Whilevoltage is applied to the both ends of the lamp 550, the mercury vapor558 can be excited such that the fluorescent material 556 emits visiblelight. The light emitted from the fluorescent material 556 is reflectedby the reflective film 554, and emits from an opening 553 of thereflective film 554. As shown in the drawing, the radial angel θ of theopening 553 is below 90 degree, and preferable in the range from about30 degree to about 90 degree.

[0056] The lamp 550 further comprises a plurality of metal grid wires590, which are disposed at the opening 553 of the reflective film 554and are parallel to the longitudinal direction of the lamp 550. Furtherreferring to FIG. 14, the metal grid wires 590 are spaced out and formedon the inside surface of the glass tube 552 such that the light with thepolarizing direction perpendicular to the metal grid wires 590 istransmitted and the light with the polarizing direction parallel to themetal grid wires 590 is reflected.

[0057] It will be apparent to those skilled in the art that thepolarized light source device is not limited to the cold cathodefluorescent lamp (CCFL). Other light source device, such as anincandescent lamp such as a halogen lamp and a discharge lamp such as axenon lamp and a neon lamp, can be provided with metal grid wires and areflective film so as to serve as a polarized light source device. Thepolarized light source device according to the present invention has anilluminant, such as a filament in an incandescent and xenon in a xenonlamp, a reflective film having an opening for projecting light, and ametal grid wire polarizer disposed at the opening for generatingpolarized light.

[0058] Now referring to FIG. 13, it depicts a polarized light source orlamp 550′ according to further another embodiment of the presentinvention. The lamp 550′ comprises a reflective film 554′ coated on theoutside surface of the glass tube 552′ and having an opening 553′. Aplurality of metal grid wires 590′ are disposed on the outside surfaceof the glass tube 552′ at the opening 553′. The function of the metalgrid wires 590′, which is similar to that of metal grid wires 590, isused for transmitting the light with the polarizing directionperpendicular to the metal grid wires 590′ and reflecting the light withthe polarizing direction parallel to the metal grid wires 590′.

[0059] Now referring to FIG. 14, it depicts metal grid wires 590 of thelamp 550 according to an embodiment of the present invention. Accordingto the present invention, the metal grid wires 590 are made of aluminum,silver, copper or alloy, and preferably are made of aluminum.Preferably, the pitch P of the metal grid wires 590 is below about 300nm, the thickness T of the metal grid wires 190 is in the range fromabout 30 nm to about 200 nm, and the ratio of the width W to the pitch Pof the metal grid wires 590 is in the range from about 0.1 to about 0.8.The metal grid wires 590 according to the present invention and thereflective film 554 can be formed on the glass tube 552 by the sameprocess at the same time. Alternatively, the metal grid wires 590 can beformed by the additional process. It will be apparent to those skilledin the art that the orientation of the metal grid wires 590 can bevaried as desired.

[0060] Referring to FIG. 15, it depicts a liquid crystal display 500using the lamp 550 according to the present invention. The liquidcrystal display 500 comprises a liquid crystal display panel 510 and aback light module 520. The liquid crystal display panel 510 comprisestwo transparent substrates 512, 514 and liquid crystal material 516disposed therebetween. The outer surfaces of transparent substrates 512,514 of the liquid crystal display panel 510 are covered with polarizingsheet 518, 519, and the inner surfaces thereof are provided withswitching elements for changing the alignments of the molecular of theliquid crystal material 516 and thus generating images.

[0061] The back light module 520 is served as a panel light device forevenly illuminating the liquid crystal display panel 510. The back lightmodule 520 comprises the above-mentioned lamp 550, a U-shaped reflector561 surrounding the lamp 550, a wedge light guide 280 and a plurality oflayers of optical films, such as diffusing sheet 540 and a prism sheet530. The diffusing sheet 540 is used for further evenly diffusing thelight. The prism sheet 530 is commercially available from 3M™ Company ofSt. Paul Minn. under the trade name Brightness Enhancement Film II (BEFII) for gathering the light in the direction perpendicular thereto.

[0062] The light emitted from the lamp 550 which has a polarizeddirection perpendicular to the longitudinal direction of the lamp 550(perpendicular to the metal grid wires 590) is transmitted into anincoming surface 584 of the light guide 580. The light guide 580 isprovided with scattering elements 582, such as a printed dot pattern ora V-shaped notched pattern on the bottom surface of the light guide 580,for scattering the light in the light guides 580 and transmitting thelight out of the upper surface or the outgoing surface 585 of the lightguide 580 so as to serve as a uniform panel light source and illuminatethe liquid crystal display panel 510. The light guide 580 is typicallymade of PMMA by the process of press or ejection molding. The lightguide 580 further comprises reflectors 560, 565 disposed in the bottomsurface and the distal end of the light guide 280 for reflecting thelight back to the light guide 580.

[0063] Furthermore, in the light guide 580, the polarizing light isscattered by the scattering elements 182 and transmitted into the liquidcrystal display panel 510. The polarization of the light which istransmitted into the liquid crystal display panel 510 is substantiallyperpendicular to the metal grid wires 590. Therefore, the light absorbedby the polarizing sheet 519 of the liquid crystal display panel 510 isdecreased so the light efficiency of the liquid crystal display 500 isincreased.

[0064] It will be apparent to those skilled in the art that thepolarizing direction of the polarizing sheet 519 on the liquid crystaldisplay panel 510 is corresponding to that of the metal grid wires 590such that the brightness of the liquid crystal display 500 is increased.Generally speaking, because of the arrangement of the liquid crystaldisplay, the back light module 520 according to the present invention isparticularly adapted to be used with a thin film transistor (TFT) liquidcrystal display panel of In-Plane-Switching, Vertical Alignment, andMulti-Domain Vertical Alignment.

[0065] Now referring to FIG. 16, it depicts a liquid crystal display 600using the lamp 550 according to the embodiment of the present invention.The liquid crystal display 600 is generally similar to the liquidcrystal display 500, wherein the similar elements are designated withthe similar reference numerals. The liquid crystal display 600 comprisesa back light guide 620 of the direct type, which has a plurality oflamps 550 disposed in a housing 670. The polarized light emitted fromthe lamp 550 can be transmitted through the polarizing sheet 619 of theliquid crystal display panel 610 and into the liquid crystal displaypanel 610. The polarized light can be transmitted through the polarizingsheet 619 of the liquid crystal display panel 610 so that the lightabsorbed by the polarizing sheet 619 is decreased and thus the lightefficiency of the liquid crystal display 600 is increased.

[0066] Although the invention has been explained in relation to itspreferred embodiment, it is not used to limit the invention. It is to beunderstood that many other possible modifications and variations can bemade by those skilled in the art without departing from the spirit andscope of the invention as hereinafter claimed.

What is claimed is:
 1. A polarized light source device comprising: alight source for generating light; a reflector surrounding the lightsource for reflecting the light and having an opening for emitting thelight; a transparent substrate disposed at the opening; anantireflection layer disposed on the transparent substrate; and aplurality of metal grid wires disposed on the antireflection layer fortransmitting the light with a predetermined polarization therethrough.2. The polarized light source device as claimed in claim 1, wherein themetal grid wires are made of aluminum.
 3. The polarized light sourcedevice as claimed in claim 1, wherein the metal grid wires are made of amaterial selected from the group consisting of aluminum, silver, copperand alloys and combinations thereof.
 4. The polarized light sourcedevice as claimed in claim 1, wherein the pitch of the metal grid wiresis below about 300 nm.
 5. The polarized light source device as claimedin claim 1, wherein the metal grid wires have a thickness in the rangefrom about 30 nm to about 200 nm.
 6. The polarized light source deviceas claimed in claim 1, wherein the ratio of the width to the pitch ofthe metal grid wires is in the range from about 0.1 to about 0.8.
 7. Thepolarized light source device as claimed in claim 1, wherein the ratioof the width to the pitch of the metal grid wires is in the range fromabout 0.5 to about 0.6.
 8. The polarized light source device as claimedin claim 1, wherein the antireflection layer is made of a material, therefractive index of which is above about 1.5.
 9. The polarized lightsource device as claimed in claim 1, wherein the antireflection layer ismade of nitrogen silicide (Si—Nx).
 10. The polarized light source deviceas claimed in claim 1, wherein the antireflection layer is a multi-layerfilm.
 11. The polarized light source device as claimed in claim 1,wherein the refractive index of the antireflection layer is in the rangebetween the refractive index of the transparent substrate and theequivalent refractive index of the metal grid wires.
 12. The polarizedlight source device as claimed in claim 1, wherein the refractive indexn_(m) of the antireflection layer is derived from the followingequation: n _(m)≈{square root}{square root over ((n _(a) ×n _(s)))}wheren_(s) is the refractive index of the transparent substrate and n_(a) isthe equivalent refractive index of the metal grid wires.
 13. Thepolarized light source device as claimed in claim 1, wherein thethickness d of the antireflection layer is derived from the followingequation: d≈¼×λ/n _(m) where n_(m) is the refractive index of theantireflection layer and λ is the wavelength of the light.
 14. A backlight module for illuminating a liquid crystal display panel of a liquidcrystal display, comprising: a polarized light source device comprising:a light source for generating light; a reflector surrounding the lightsource for reflecting the light and having an opening for emitting thelight; a transparent substrate disposed at the opening; anantireflection layer disposed on the transparent substrate; and aplurality of metal grid wires disposed on the antireflection layer fortransmitting the light with a predetermined polarization therethrough;and a light guide having at least one incoming surface facing thepolarized light source, a plurality of scattering elements, and anoutgoing surface, wherein the light emitted from the polarized lightsource is transmitted into the light guide from the incoming surface,scattered by the scattering elements, and then transmitted out of thelight guide from the outgoing surface.
 15. The back light module asclaimed in claim 14, further comprising: a plurality of optical filmsdisposed between the outgoing surface of the light guide and the liquidcrystal display panel.
 16. The back light module as claimed in claim 15,wherein the optical films comprise: at least one diffusing sheet fordiffusing the light emitted from the light guide; and at least one prismsheet for gathering the light in the direction perpendicular thereto.17. The back light module as claimed in claim 14, wherein the metal gridwires are made of aluminum.
 18. The back light module as claimed inclaim 14, wherein the metal grid wires are made of a material selectedfrom the group consisting of aluminum, silver, copper and alloys andcombinations thereof.
 19. The back light module as claimed in claim 14,wherein the pitch of the metal grid wires is below about 300 nm.
 20. Theback light module as claimed in claim 14, wherein the metal grid wireshave a thickness in the range from about 30 nm to about 200 nm.
 21. Theback light module as claimed in claim 14, wherein the ratio of the widthto the pitch of the metal grid wires is in the range from about 0.1 toabout 0.8.
 22. The back light module as claimed in claim 14, wherein theratio of the width to the pitch of the metal grid wires is in the rangefrom about 0.5 to about 0.6.
 23. The back light module as claimed inclaim 14, wherein the antireflection layer is made of a material, therefractive index of which is above about 1.5.
 24. The back light moduleas claimed in claim 14, wherein the antireflection layer is made ofnitrogen silicide (Si—Nx).
 25. The back light module as claimed in claim14, wherein the antireflection layer is a multi-layer film.
 26. The backlight module as claimed in claim 14, wherein the refractive index of theantireflection layer is in the range between the refractive index of thetransparent substrate and the equivalent refractive index of the metalgrid wires.
 27. The back light module as claimed in claim 14, whereinthe refractive index n_(m) of the antireflection layer is derived fromthe following equation: n _(m)≈{square root}{square root over ((n _(a)×n _(s)))}where n_(s) is the refractive index of the transparentsubstrate and n_(a) is the equivalent refractive index of the metal gridwires.
 28. The back light module as claimed in claim 14, wherein thethickness d of the antireflection layer is derived from the followingequation: d≈¼×λ/n _(m) where n_(m) is the refractive index of theantireflection layer and λ is the wavelength of the light emitted fromthe light source.
 29. A liquid crystal display, comprising: a liquidcrystal display panel; and at least one polarized light source forilluminating the liquid crystal display panel, comprising: a lightsource for generating light; a reflector surrounding the light sourcefor reflecting the light and having an opening for emitting the light; atransparent substrate disposed at the opening; an antireflection layerdisposed on the transparent substrate; and a plurality of metal gridwires disposed on the antireflection layer for transmitting the lightwith a predetermined polarization therethrough.
 30. The liquid crystaldisplay as claimed in claim 29, further comprising: a plurality ofoptical films disposed between the light source and the liquid crystaldisplay panel.
 31. The liquid crystal display as claimed in claim 30,wherein the optical films comprise: at least one diffusing sheet fordiffusing the light emitted from the light guide; and at least one prismsheet for gathering the light in the direction perpendicular thereto.32. The liquid crystal display as claimed in claim 29, wherein the metalgrid wires are made of aluminum.
 33. The liquid crystal display asclaimed in claim 29, wherein the metal grid wires are made of a materialselected from the group consisting of aluminum, silver, copper andalloys and combinations thereof.
 34. The liquid crystal display asclaimed in claim 29, wherein the pitch of the metal grid wires is belowabout 300 nm.
 35. The liquid crystal display as claimed in claim 29,wherein the metal grid wires have a thickness in the range from about 30nm to about 200 nm.
 36. The liquid crystal display as claimed in claim29, wherein the ratio of the width to the pitch of the metal grid wiresis in the range from about 0.1 to about 0.8.
 37. The liquid crystaldisplay as claimed in claim 29, wherein the ratio of the width to thepitch of the metal grid wires is in the range from about 0.5 to about0.6.
 38. The liquid crystal display as claimed in claim 29, wherein theantireflection layer is made of a material, the refractive index ofwhich is above about 1.5.
 39. The liquid crystal display as claimed inclaim 29, wherein the antireflection layer is made of nitrogen silicide(Si—Nx).
 40. The liquid crystal display as claimed in claim 29, whereinthe antireflection layer is a multi-layer film.
 41. The liquid crystaldisplay as claimed in claim 29, wherein the refractive index of theantireflection layer is in the range between the refractive index of thetransparent substrate and the equivalent refractive index of the metalgrid wires.
 42. The liquid crystal display as claimed in claim 29,wherein the refractive index n_(m) of the antireflection layer isderived from the following equation: n _(m)≈{square root}{square rootover ((n _(a) ×n _(s)))}where n_(s) is the refractive index of thetransparent substrate and n_(a) is the equivalent refractive index ofthe metal grid wires.
 43. The liquid crystal display as claimed in claim29, wherein the thickness d of the antireflection layer is derived fromthe following equation: d≈¼×λ/n _(m) where n_(m) is the refractive indexof the antireflection layer and λ is the wavelength of the light emittedfrom the light source.
 44. A polarized light source, comprising: anilluminant for generating light; a reflective film surrounding theilluminant and having an opening for emitting the light; and a pluralityof metal grid wires disposed at the opening for transmitting the lightwith a predetermined polarization therethrough.
 45. The polarized lightsource as claimed in claim 44, wherein the metal grid wires are made ofaluminum.
 46. The polarized light source as claimed in claim 44, whereinthe metal grid wires are made of a material selected from the groupconsisting of aluminum, silver, copper and alloys and combinationsthereof.
 47. The polarized light source as claimed in claim 44, whereinthe pitch of the metal grid wires is below about 300 nm.
 48. Thepolarized light source as claimed in claim 44, wherein the metal gridwires have a thickness in the range from about 30 nm to about 200 nm.49. The polarized light source as claimed in claim 44, wherein the ratioof the width to the pitch of the metal grid wires is in the range fromabout 0.1 to about 0.8.
 50. The polarized light source as claimed inclaim 44, wherein the illuminant comprises a transparent tube, mercuryvapor filling the transparent tube, and a fluorescent material disposedon the transparent tube, and the reflective film and the metal gridwires are disposed on the transparent tube.
 51. The polarized lightsource as claimed in claim 50, wherein the reflective film and the metalgrid wires are disposed on the inside surface of the transparent tubebetween the fluorescent material and the transparent tube.
 52. Thepolarized light source as claimed in claim 50, wherein the reflectivefilm and the metal grid wires are disposed on the outside surface of thetransparent tube.
 53. The polarized light source as claimed in claim 50,wherein the transparent tube is a substantially elongated round tube,the opening of the reflective film extends along the axial direction ofthe transparent tube, and the radial angel of the opening is below 90degree.
 54. The polarized light source as claimed in claim 50, whereinthe transparent tube is a substantially elongated round tube, theopening of the reflective film extends along the axial direction of thetransparent tube, and the radial angel of the opening is in the rangefrom about 30 degree to about 90 degree.
 55. The polarized light sourceas claimed in claim 44, further comprising a transparent substrate,wherein the reflective film and the metal grid wires are formed on thetransparent substrate by a process.
 56. A back light module forilluminating a liquid crystal display panel of a liquid crystal display,comprising: a light source, comprising: an illuminant for generatinglight; a reflective film surrounding the illuminant and having anopening for emitting the light; and a plurality of metal grid wiresdisposed at the opening for transmitting the light with a predeterminedpolarization therethrough; a light guide disposed under the liquidcrystal display panel and having at least one incoming surface facingthe polarized light source, a plurality of scattering elements, and anoutgoing surface, wherein the light emitted from the polarized lightsource is transmitted into the light guide from the incoming surface,scattered by the scattering elements, and then transmitted out of thelight guide from the outgoing surface; and a plurality of optical filmsdisposed between the outgoing surface of the light guide and the liquidcrystal display panel.
 57. The back light module as claimed in claim 56,further comprising a reflector surrounding the light source.
 58. Theback light module as claimed in claim 56, wherein the metal grid wiresare made of aluminum.
 59. The back light module as claimed in claim 56,wherein the metal grid wires are made of a material selected from thegroup consisting of aluminum, silver, copper and alloys and combinationsthereof.
 60. The back light module as claimed in claim 56, wherein thepitch of the metal grid wires is below about 300 nm.
 61. The back lightmodule as claimed in claim 56, wherein the metal grid wires have athickness in the range from about 30 nm to about 200 nm.
 62. The backlight module as claimed in claim 56, wherein the ratio of the width tothe pitch of the metal grid wires is in the range from about 0.1 toabout 0.8.
 63. The back light module as claimed in claim 56, wherein theoptical films comprise: at least one diffusing sheet for diffusing thelight emitted from the light guide; and at least one prism sheet forgathering the light in the direction perpendicular thereto.
 64. A backlight module for illuminating a liquid crystal display panel of a liquidcrystal display, comprising: at least one light source, comprising: anilluminant disposed under the liquid crystal display panel forgenerating light; a reflective film surrounding the illuminant andhaving an opening for emitting the light; and a plurality of metal gridwires disposed at the opening for transmitting the light with apredetermined polarization therethrough; and a plurality of opticalfilms disposed between the light source and the liquid crystal displaypanel.
 65. The back light module as claimed in claim 64, furthercomprising a reflector surrounding the light source.
 66. The back lightmodule as claimed in claim 64, wherein the metal grid wires are made ofaluminum.
 67. The back light module as claimed in claim 64, wherein themetal grid wires are made of a material selected from the groupconsisting of aluminum, silver, copper and alloys and combinationsthereof.
 68. The back light module as claimed in claim 64, wherein thepitch of the metal grid wires is below about 300 nm.
 69. The back lightmodule as claimed in claim 64, wherein the metal grid wires have athickness in the range from about 30 nm to about 200 nm.
 70. The backlight module as claimed in claim 64, wherein the ratio of the width tothe pitch of the metal grid wires is in the range from about 0.1 toabout 0.8.
 71. The back light module as claimed in claim 64, wherein theoptical films comprise: at least one diffusing sheet for diffusing thelight emitted from the light guide; and at least one prism sheet forgathering the light in the direction perpendicular thereto.